1. Technical Field
The present invention relates to linear transmissions, and more particularly relates to a ball screw with support devices.
2. Description of Related Art
Generally speaking, ball screws have been extensively used for transmissions where precision is of high priority, and the length of the screw of a ball screw is increased with the travel of the transmission. However, a long screw with a large slenderness ratio tends to have gravity sag due to its own weight. Such sag can significantly degrade the precision of the transmission, and has adversely effect on the service life of the screw, thus being a problem to address.
FIG. 1 depicts a conventional ball screw 10, which primarily comprises a screw 11 and a nut 12. The nut 12 is fixed to a nut brace 13 and is mounted around the screw 11.
At two sides of the nut brace 13, support devices 14 are provided. The support device 14 comprises a bush 141 fixed to a bush seat 142 and mounted around the screw 11. The nut brace 13 and the support devices 14 are further equipped with a first pulley 15 and a second pulley 16 that drive displacement, so that when the nut brace 13 moves, the bush seats 142 are displaced simultaneously, thereby ensuring that the bush seats 142 are always well positioned at two sides of the nut brace 13 for providing support. While the first pulley 15 and the second pulley 16 do help to ensure stable displacement of the nut brace 13 and the bush seat 142 and reliable support to the screw, the overall configuration is structurally complicated and the maintenance thereof is costly.
In view of this, the inventor of the present invention has conducted extensive research, study and experiments as well as tests, and now successfully invents a ball screw equipped with novel support devices.